xenbus_probe.c

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/******************************************************************************
 * Talks to Xen Store to figure out what devices we have.
 *
 * Copyright (C) 2005 Rusty Russell, IBM Corporation
 * Copyright (C) 2005 Mike Wray, Hewlett-Packard
 * Copyright (C) 2005, 2006 XenSource Ltd
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#define DPRINTK(fmt, args...)               \
    pr_debug("xenbus_probe (%s:%d) " fmt ".\n", \
         __func__, __LINE__, ##args)

#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/notifier.h>
#include <linux/kthread.h>
#include <linux/mutex.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/module.h>

#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/xen/hypervisor.h>

#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <xen/page.h>

#include <xen/hvm.h>

#include "xenbus_comms.h"
#include "xenbus_probe.h"


int xen_store_evtchn;
EXPORT_SYMBOL_GPL(xen_store_evtchn);

struct xenstore_domain_interface *xen_store_interface;
EXPORT_SYMBOL_GPL(xen_store_interface);

static unsigned long xen_store_mfn;

static BLOCKING_NOTIFIER_HEAD(xenstore_chain);

/* If something in array of ids matches this device, return it. */
static const struct xenbus_device_id *
match_device(const struct xenbus_device_id *arr, struct xenbus_device *dev)
{
    for (; *arr->devicetype != '\0'; arr++) {
        if (!strcmp(arr->devicetype, dev->devicetype))
            return arr;
    }
    return NULL;
}

int xenbus_match(struct device *_dev, struct device_driver *_drv)
{
    struct xenbus_driver *drv = to_xenbus_driver(_drv);

    if (!drv->ids)
        return 0;

    return match_device(drv->ids, to_xenbus_device(_dev)) != NULL;
}
EXPORT_SYMBOL_GPL(xenbus_match);


static void free_otherend_details(struct xenbus_device *dev)
{
    kfree(dev->otherend);
    dev->otherend = NULL;
}


static void free_otherend_watch(struct xenbus_device *dev)
{
    if (dev->otherend_watch.node) {
        unregister_xenbus_watch(&dev->otherend_watch);
        kfree(dev->otherend_watch.node);
        dev->otherend_watch.node = NULL;
    }
}


static int talk_to_otherend(struct xenbus_device *dev)
{
    struct xenbus_driver *drv = to_xenbus_driver(dev->dev.driver);

    free_otherend_watch(dev);
    free_otherend_details(dev);

    return drv->read_otherend_details(dev);
}



static int watch_otherend(struct xenbus_device *dev)
{
    struct xen_bus_type *bus =
        container_of(dev->dev.bus, struct xen_bus_type, bus);

    return xenbus_watch_pathfmt(dev, &dev->otherend_watch,
                    bus->otherend_changed,
                    "%s/%s", dev->otherend, "state");
}


int xenbus_read_otherend_details(struct xenbus_device *xendev,
                 char *id_node, char *path_node)
{
    int err = xenbus_gather(XBT_NIL, xendev->nodename,
                id_node, "%i", &xendev->otherend_id,
                path_node, NULL, &xendev->otherend,
                NULL);
    if (err) {
        xenbus_dev_fatal(xendev, err,
                 "reading other end details from %s",
                 xendev->nodename);
        return err;
    }
    if (strlen(xendev->otherend) == 0 ||
        !xenbus_exists(XBT_NIL, xendev->otherend, "")) {
        xenbus_dev_fatal(xendev, -ENOENT,
                 "unable to read other end from %s.  "
                 "missing or inaccessible.",
                 xendev->nodename);
        free_otherend_details(xendev);
        return -ENOENT;
    }

    return 0;
}
EXPORT_SYMBOL_GPL(xenbus_read_otherend_details);

void xenbus_otherend_changed(struct xenbus_watch *watch,
                 const char **vec, unsigned int len,
                 int ignore_on_shutdown)
{
    struct xenbus_device *dev =
        container_of(watch, struct xenbus_device, otherend_watch);
    struct xenbus_driver *drv = to_xenbus_driver(dev->dev.driver);
    enum xenbus_state state;

    /* Protect us against watches firing on old details when the otherend
       details change, say immediately after a resume. */
    if (!dev->otherend ||
        strncmp(dev->otherend, vec[XS_WATCH_PATH],
            strlen(dev->otherend))) {
        dev_dbg(&dev->dev, "Ignoring watch at %s\n",
            vec[XS_WATCH_PATH]);
        return;
    }

    state = xenbus_read_driver_state(dev->otherend);

    dev_dbg(&dev->dev, "state is %d, (%s), %s, %s\n",
        state, xenbus_strstate(state), dev->otherend_watch.node,
        vec[XS_WATCH_PATH]);

    /*
     * Ignore xenbus transitions during shutdown. This prevents us doing
     * work that can fail e.g., when the rootfs is gone.
     */
    if (system_state > SYSTEM_RUNNING) {
        if (ignore_on_shutdown && (state == XenbusStateClosing))
            xenbus_frontend_closed(dev);
        return;
    }

    if (drv->otherend_changed)
        drv->otherend_changed(dev, state);
}
EXPORT_SYMBOL_GPL(xenbus_otherend_changed);

int xenbus_dev_probe(struct device *_dev)
{
    struct xenbus_device *dev = to_xenbus_device(_dev);
    struct xenbus_driver *drv = to_xenbus_driver(_dev->driver);
    const struct xenbus_device_id *id;
    int err;

    DPRINTK("%s", dev->nodename);

    if (!drv->probe) {
        err = -ENODEV;
        goto fail;
    }

    id = match_device(drv->ids, dev);
    if (!id) {
        err = -ENODEV;
        goto fail;
    }

    err = talk_to_otherend(dev);
    if (err) {
        dev_warn(&dev->dev, "talk_to_otherend on %s failed.\n",
             dev->nodename);
        return err;
    }

    err = drv->probe(dev, id);
    if (err)
        goto fail;

    err = watch_otherend(dev);
    if (err) {
        dev_warn(&dev->dev, "watch_otherend on %s failed.\n",
               dev->nodename);
        return err;
    }

    return 0;
fail:
    xenbus_dev_error(dev, err, "xenbus_dev_probe on %s", dev->nodename);
    xenbus_switch_state(dev, XenbusStateClosed);
    return err;
}
EXPORT_SYMBOL_GPL(xenbus_dev_probe);

int xenbus_dev_remove(struct device *_dev)
{
    struct xenbus_device *dev = to_xenbus_device(_dev);
    struct xenbus_driver *drv = to_xenbus_driver(_dev->driver);

    DPRINTK("%s", dev->nodename);

    free_otherend_watch(dev);

    if (drv->remove)
        drv->remove(dev);

    free_otherend_details(dev);

    xenbus_switch_state(dev, XenbusStateClosed);
    return 0;
}
EXPORT_SYMBOL_GPL(xenbus_dev_remove);

void xenbus_dev_shutdown(struct device *_dev)
{
    struct xenbus_device *dev = to_xenbus_device(_dev);
    unsigned long timeout = 5*HZ;

    DPRINTK("%s", dev->nodename);

    get_device(&dev->dev);
    if (dev->state != XenbusStateConnected) {
        printk(KERN_INFO "%s: %s: %s != Connected, skipping\n", __func__,
               dev->nodename, xenbus_strstate(dev->state));
        goto out;
    }
    xenbus_switch_state(dev, XenbusStateClosing);
    timeout = wait_for_completion_timeout(&dev->down, timeout);
    if (!timeout)
        printk(KERN_INFO "%s: %s timeout closing device\n",
               __func__, dev->nodename);
 out:
    put_device(&dev->dev);
}
EXPORT_SYMBOL_GPL(xenbus_dev_shutdown);

int xenbus_register_driver_common(struct xenbus_driver *drv,
                  struct xen_bus_type *bus)
{
    drv->driver.bus = &bus->bus;

    return driver_register(&drv->driver);
}
EXPORT_SYMBOL_GPL(xenbus_register_driver_common);

void xenbus_unregister_driver(struct xenbus_driver *drv)
{
    driver_unregister(&drv->driver);
}
EXPORT_SYMBOL_GPL(xenbus_unregister_driver);

struct xb_find_info {
    struct xenbus_device *dev;
    const char *nodename;
};

static int cmp_dev(struct device *dev, void *data)
{
    struct xenbus_device *xendev = to_xenbus_device(dev);
    struct xb_find_info *info = data;

    if (!strcmp(xendev->nodename, info->nodename)) {
        info->dev = xendev;
        get_device(dev);
        return 1;
    }
    return 0;
}

static struct xenbus_device *xenbus_device_find(const char *nodename,
                        struct bus_type *bus)
{
    struct xb_find_info info = { .dev = NULL, .nodename = nodename };

    bus_for_each_dev(bus, NULL, &info, cmp_dev);
    return info.dev;
}

static int cleanup_dev(struct device *dev, void *data)
{
    struct xenbus_device *xendev = to_xenbus_device(dev);
    struct xb_find_info *info = data;
    int len = strlen(info->nodename);

    DPRINTK("%s", info->nodename);

    /* Match the info->nodename path, or any subdirectory of that path. */
    if (strncmp(xendev->nodename, info->nodename, len))
        return 0;

    /* If the node name is longer, ensure it really is a subdirectory. */
    if ((strlen(xendev->nodename) > len) && (xendev->nodename[len] != '/'))
        return 0;

    info->dev = xendev;
    get_device(dev);
    return 1;
}

static void xenbus_cleanup_devices(const char *path, struct bus_type *bus)
{
    struct xb_find_info info = { .nodename = path };

    do {
        info.dev = NULL;
        bus_for_each_dev(bus, NULL, &info, cleanup_dev);
        if (info.dev) {
            device_unregister(&info.dev->dev);
            put_device(&info.dev->dev);
        }
    } while (info.dev);
}

static void xenbus_dev_release(struct device *dev)
{
    if (dev)
        kfree(to_xenbus_device(dev));
}

static ssize_t nodename_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%s\n", to_xenbus_device(dev)->nodename);
}

static ssize_t devtype_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%s\n", to_xenbus_device(dev)->devicetype);
}

static ssize_t modalias_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%s:%s\n", dev->bus->name,
               to_xenbus_device(dev)->devicetype);
}

struct device_attribute xenbus_dev_attrs[] = {
    __ATTR_RO(nodename),
    __ATTR_RO(devtype),
    __ATTR_RO(modalias),
    __ATTR_NULL
};
EXPORT_SYMBOL_GPL(xenbus_dev_attrs);

int xenbus_probe_node(struct xen_bus_type *bus,
              const char *type,
              const char *nodename)
{
    char devname[XEN_BUS_ID_SIZE];
    int err;
    struct xenbus_device *xendev;
    size_t stringlen;
    char *tmpstring;

    enum xenbus_state state = xenbus_read_driver_state(nodename);

    if (state != XenbusStateInitialising) {
        /* Device is not new, so ignore it.  This can happen if a
           device is going away after switching to Closed.  */
        return 0;
    }

    stringlen = strlen(nodename) + 1 + strlen(type) + 1;
    xendev = kzalloc(sizeof(*xendev) + stringlen, GFP_KERNEL);
    if (!xendev)
        return -ENOMEM;

    xendev->state = XenbusStateInitialising;

    /* Copy the strings into the extra space. */

    tmpstring = (char *)(xendev + 1);
    strcpy(tmpstring, nodename);
    xendev->nodename = tmpstring;

    tmpstring += strlen(tmpstring) + 1;
    strcpy(tmpstring, type);
    xendev->devicetype = tmpstring;
    init_completion(&xendev->down);

    xendev->dev.bus = &bus->bus;
    xendev->dev.release = xenbus_dev_release;

    err = bus->get_bus_id(devname, xendev->nodename);
    if (err)
        goto fail;

    dev_set_name(&xendev->dev, devname);

    /* Register with generic device framework. */
    err = device_register(&xendev->dev);
    if (err)
        goto fail;

    return 0;
fail:
    kfree(xendev);
    return err;
}
EXPORT_SYMBOL_GPL(xenbus_probe_node);

static int xenbus_probe_device_type(struct xen_bus_type *bus, const char *type)
{
    int err = 0;
    char **dir;
    unsigned int dir_n = 0;
    int i;

    dir = xenbus_directory(XBT_NIL, bus->root, type, &dir_n);
    if (IS_ERR(dir))
        return PTR_ERR(dir);

    for (i = 0; i < dir_n; i++) {
        err = bus->probe(bus, type, dir[i]);
        if (err)
            break;
    }

    kfree(dir);
    return err;
}

int xenbus_probe_devices(struct xen_bus_type *bus)
{
    int err = 0;
    char **dir;
    unsigned int i, dir_n;

    dir = xenbus_directory(XBT_NIL, bus->root, "", &dir_n);
    if (IS_ERR(dir))
        return PTR_ERR(dir);

    for (i = 0; i < dir_n; i++) {
        err = xenbus_probe_device_type(bus, dir[i]);
        if (err)
            break;
    }

    kfree(dir);
    return err;
}
EXPORT_SYMBOL_GPL(xenbus_probe_devices);

static unsigned int char_count(const char *str, char c)
{
    unsigned int i, ret = 0;

    for (i = 0; str[i]; i++)
        if (str[i] == c)
            ret++;
    return ret;
}

static int strsep_len(const char *str, char c, unsigned int len)
{
    unsigned int i;

    for (i = 0; str[i]; i++)
        if (str[i] == c) {
            if (len == 0)
                return i;
            len--;
        }
    return (len == 0) ? i : -ERANGE;
}

void xenbus_dev_changed(const char *node, struct xen_bus_type *bus)
{
    int exists, rootlen;
    struct xenbus_device *dev;
    char type[XEN_BUS_ID_SIZE];
    const char *p, *root;

    if (char_count(node, '/') < 2)
        return;

    exists = xenbus_exists(XBT_NIL, node, "");
    if (!exists) {
        xenbus_cleanup_devices(node, &bus->bus);
        return;
    }

    /* backend/<type>/... or device/<type>/... */
    p = strchr(node, '/') + 1;
    snprintf(type, XEN_BUS_ID_SIZE, "%.*s", (int)strcspn(p, "/"), p);
    type[XEN_BUS_ID_SIZE-1] = '\0';

    rootlen = strsep_len(node, '/', bus->levels);
    if (rootlen < 0)
        return;
    root = kasprintf(GFP_KERNEL, "%.*s", rootlen, node);
    if (!root)
        return;

    dev = xenbus_device_find(root, &bus->bus);
    if (!dev)
        xenbus_probe_node(bus, type, root);
    else
        put_device(&dev->dev);

    kfree(root);
}
EXPORT_SYMBOL_GPL(xenbus_dev_changed);

int xenbus_dev_suspend(struct device *dev)
{
    int err = 0;
    struct xenbus_driver *drv;
    struct xenbus_device *xdev
        = container_of(dev, struct xenbus_device, dev);

    DPRINTK("%s", xdev->nodename);

    if (dev->driver == NULL)
        return 0;
    drv = to_xenbus_driver(dev->driver);
    if (drv->suspend)
        err = drv->suspend(xdev);
    if (err)
        printk(KERN_WARNING
               "xenbus: suspend %s failed: %i\n", dev_name(dev), err);
    return 0;
}
EXPORT_SYMBOL_GPL(xenbus_dev_suspend);

int xenbus_dev_resume(struct device *dev)
{
    int err;
    struct xenbus_driver *drv;
    struct xenbus_device *xdev
        = container_of(dev, struct xenbus_device, dev);

    DPRINTK("%s", xdev->nodename);

    if (dev->driver == NULL)
        return 0;
    drv = to_xenbus_driver(dev->driver);
    err = talk_to_otherend(xdev);
    if (err) {
        printk(KERN_WARNING
               "xenbus: resume (talk_to_otherend) %s failed: %i\n",
               dev_name(dev), err);
        return err;
    }

    xdev->state = XenbusStateInitialising;

    if (drv->resume) {
        err = drv->resume(xdev);
        if (err) {
            printk(KERN_WARNING
                   "xenbus: resume %s failed: %i\n",
                   dev_name(dev), err);
            return err;
        }
    }

    err = watch_otherend(xdev);
    if (err) {
        printk(KERN_WARNING
               "xenbus_probe: resume (watch_otherend) %s failed: "
               "%d.\n", dev_name(dev), err);
        return err;
    }

    return 0;
}
EXPORT_SYMBOL_GPL(xenbus_dev_resume);

int xenbus_dev_cancel(struct device *dev)
{
    /* Do nothing */
    DPRINTK("cancel");
    return 0;
}
EXPORT_SYMBOL_GPL(xenbus_dev_cancel);

/* A flag to determine if xenstored is 'ready' (i.e. has started) */
int xenstored_ready;


int register_xenstore_notifier(struct notifier_block *nb)
{
    int ret = 0;

    if (xenstored_ready > 0)
        ret = nb->notifier_call(nb, 0, NULL);
    else
        blocking_notifier_chain_register(&xenstore_chain, nb);

    return ret;
}
EXPORT_SYMBOL_GPL(register_xenstore_notifier);

void unregister_xenstore_notifier(struct notifier_block *nb)
{
    blocking_notifier_chain_unregister(&xenstore_chain, nb);
}
EXPORT_SYMBOL_GPL(unregister_xenstore_notifier);

void xenbus_probe(struct work_struct *unused)
{
    xenstored_ready = 1;

    /* Notify others that xenstore is up */
    blocking_notifier_call_chain(&xenstore_chain, 0, NULL);
}
EXPORT_SYMBOL_GPL(xenbus_probe);

static int __init xenbus_probe_initcall(void)
{
    if (!xen_domain())
        return -ENODEV;

    if (xen_initial_domain() || xen_hvm_domain())
        return 0;

    xenbus_probe(NULL);
    return 0;
}

device_initcall(xenbus_probe_initcall);

/* Set up event channel for xenstored which is run as a local process
 * (this is normally used only in dom0)
 */
static int __init xenstored_local_init(void)
{
    int err = 0;
    unsigned long page = 0;
    struct evtchn_alloc_unbound alloc_unbound;

    /* Allocate Xenstore page */
    page = get_zeroed_page(GFP_KERNEL);
    if (!page)
        goto out_err;

    xen_store_mfn = xen_start_info->store_mfn =
        pfn_to_mfn(virt_to_phys((void *)page) >>
               PAGE_SHIFT);

    /* Next allocate a local port which xenstored can bind to */
    alloc_unbound.dom        = DOMID_SELF;
    alloc_unbound.remote_dom = DOMID_SELF;

    err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
                      &alloc_unbound);
    if (err == -ENOSYS)
        goto out_err;

    BUG_ON(err);
    xen_store_evtchn = xen_start_info->store_evtchn =
        alloc_unbound.port;

    return 0;

 out_err:
    if (page != 0)
        free_page(page);
    return err;
}

enum xenstore_init {
    UNKNOWN,
    PV,
    HVM,
    LOCAL,
};
static int __init xenbus_init(void)
{
    int err = 0;
    enum xenstore_init usage = UNKNOWN;
    uint64_t v = 0;

    if (!xen_domain())
        return -ENODEV;

    xenbus_ring_ops_init();

    if (xen_pv_domain())
        usage = PV;
    if (xen_hvm_domain())
        usage = HVM;
    if (xen_hvm_domain() && xen_initial_domain())
        usage = LOCAL;
    if (xen_pv_domain() && !xen_start_info->store_evtchn)
        usage = LOCAL;
    if (xen_pv_domain() && xen_start_info->store_evtchn)
        xenstored_ready = 1;

    switch (usage) {
    case LOCAL:
        err = xenstored_local_init();
        if (err)
            goto out_error;
        xen_store_interface = mfn_to_virt(xen_store_mfn);
        break;
    case PV:
        xen_store_evtchn = xen_start_info->store_evtchn;
        xen_store_mfn = xen_start_info->store_mfn;
        xen_store_interface = mfn_to_virt(xen_store_mfn);
        break;
    case HVM:
        err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
        if (err)
            goto out_error;
        xen_store_evtchn = (int)v;
        err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
        if (err)
            goto out_error;
        xen_store_mfn = (unsigned long)v;
        xen_store_interface =
            ioremap(xen_store_mfn << PAGE_SHIFT, PAGE_SIZE);
        break;
    default:
        pr_warn("Xenstore state unknown\n");
        break;
    }

    /* Initialize the interface to xenstore. */
    err = xs_init();
    if (err) {
        printk(KERN_WARNING
               "XENBUS: Error initializing xenstore comms: %i\n", err);
        goto out_error;
    }

#ifdef CONFIG_XEN_COMPAT_XENFS
    /*
     * Create xenfs mountpoint in /proc for compatibility with
     * utilities that expect to find "xenbus" under "/proc/xen".
     */
    proc_mkdir("xen", NULL);
#endif

out_error:
    return err;
}

postcore_initcall(xenbus_init);

MODULE_LICENSE("GPL");